Quantum plasmonics: Symmetry-dependent plasmon-molecule coupling and quantized photoconductances

We investigate photoinduced electron transport through nanoparticle dimers connected by linear and ringlikemolecules. The two model junctions exhibit similar absorption but distinct photoconductance. The linear-chainjunction shows a constant conductance that is independent of photon energies. In contrast, the ring moleculesshow quantized conductance resonances at energies corresponding to the molecular excitations. These resultscan be understood from the symmetry and quantization of local molecular excitations, and have implications forplasmon-molecule interactions in general